Hitherto, as a method for crosslinking and curing an epoxy compound by an ultraviolet ray or heating in a short time of period, there has been known a composition having an ionic polymerizability. In order to improve physical properties of a coating layer from the composition, there has been investigated a method employing a variety of compounds.
Such an ionic curing system, particularly, a cationic curing system can be employed for coating a metal and plastics and, in recent years, it has been investigated as uses for coating metal cans, and drawn metal cans coated with plastic films.
However, in the composition containing ionic catalysts, since storage stability is not good so much, a variety of methods have been investigated. For example, JP-A-06073163 Official Gazette proposes a method in which an organic phosphine is molded into a microcapsule by wrapping in a particle-state using a polymer.
Further, there is a method in which one-liquid storage stability is attained by allowing to adsorb it in a compound such as a zeolite having pores. However, a latent property described hereinafter is insufficient in such catalyst systems, and uses are limited because of a heterogeneous system and being incapable of employing for a method such as impregnation.
Further, it has a drawback that a cured resin is apt to become not uniform.
On the other hand, there is widely investigated a method using a thermally latent catalyst in which an activity in the acidic catalyst is temporarily suppressed, and there is shown again the activity by cleavage thereof during heating and curing. As such the latent catalyst, for example, there are known a catalyst blocking an active proton by utilizing a neutralization reaction of an acid-base and a catalyst blocking an active proton by utilizing an esterification reaction of an acid with alcohols in JP-B-77000770 Official Gazette. Further, there are known benzyl sulphonium salt type and benzyl piridinium salt type catalysts which are a thermal latent catalyst which produces an active benzyl cation by thermal decomposition of an onium salt in JP-A-62192427 Official Gazette.
Still further, as commercially supplied thermal latent acidic catalysts, there are enumerated a monoethylamine complex of boron trifluoride and piridinium complex of boron trifluoride which are a Lewis acid.
However, in the catalyst utilizing a neutralization reaction of an acid-base and the catalyst utilizing an esterification reaction of an acid with alcohols, it is difficult to obtain a thermal latent acidic catalyst in which there are consistent an appropriate dissociation temperature and thermal stability of the catalyst itself. Furthermore, in the benzyl sulphonium salt type and benzyl piridinium salt type catalysts, although a storage stability is relatively excellent, it is not sufficient and, particularly, in the case that it is employed together with cycloaliphatic epoxide having high reactivity, a storage stability is worse.
As described hereinabove, in the case that conventional catalysts for curing are employed together with epoxy resins, a reaction gradually progresses even at room temperatures from immediately after the catalyst is mixed with the epoxy resins which are resin components for curing. For that reason, storage time of period is limited in an epoxy resin composition, and it must be ended to employ within the period.
On the other hand, as a cationic polymerization catalyst for a cationic polymerizable vinyl compound, although there have been conventionally known Lewis acids such as BF3, a storage stability is exceedingly worse because a reaction is caused even at a temperature such as room temperatures. Further, a polymerization reaction cannot be readily controlled, and polymerization degree is low in a resin obtained. In order to allow to polymerize a vinyl compound, polymerization is conducted by feeding a catalyst after cooling monomer containing an appropriate solvent to an exceedingly low fixed temperature. However, operations are troublesome for conducting a polymerization reaction at the exceedingly low temperature, and it requires costs.
Further, in the case of employing conventional catalysts, since curing is caused by an ionic reaction in an epoxy compound and an acrylic resin to be employed in the present inventions (i) to (v), ionic catalysts are remained in a cured resin after reaction, and there is caused a problem that an electric insulation property lowers in the resin.
Still further, in coating for vehicles such as cars, a cationic electro-deposition coating and an intermediate coating are coated on an outside plate such as a metal and plastics, and then, there is coated a finishing coating such as an opaque coloring coating, a transparent coloring coating, and a clear coating. In the case that the vehicles are placed outside in summer season, temperature elevates to 50-70° C. or so, and coatings are softened and apt to become deteriorated. Accordingly, there are required heat resistance, staining resistance, and abrasion resistance, etc. in a coating layer from the finishing coating.
As the finishing coating, particularly, a clear coating, there is employed a solvent-based coating composed of an acrylic resin having hydroxyl groups and a melamine resin. However, although a coating layer thereof is excellent in weatherability and finishing outer appearance, acid rain resistance is not sufficient.
As a coating in which acid rain resistance is improved, although there is employed a solvent-based coating (an acid-epoxy type coating) composed of a resin having carboxylic groups and a resin having epoxy groups, it is poor in staining resistance and, further, it is apt to be stained by adherence and soaking of dusts and sands, exhausted components, staining substances caused by animals and vegetables, and iron powder, etc.
On the other hand, as a method for crosslinking and curing an epoxy compound within a short time of period by an ultraviolet ray and heat, an ionic polymerizable composition has been known.
However, in the composition containing an ionic catalyst, since storage stability is not good so much, as illustrated hereinabove in detail, although a variety of methods are investigated, a sufficiently satisfied method is not still found out.
Further, in recent years, a shift to a high integration or high arithmetic speed is advanced in electronics equipments such as a large-scale computer with a progress in an electronics-information technology. As a result, for an object of the high integration even in a printed circuit board, a laminated printed circuit board is becoming highlighted in which laminated circuits are formed. The laminated printed circuit board is shifting to a direction of further high integration with a progress of a shift of the electronics equipments to small-sizing and multi functions.
That is, a circuit is shifting to micro wiring, and a via-hole is shifting to small diameter, thinning, and highly multi-laminating.
Hitherto, the laminated printed circuit board is prepared through a step in which there is laminated a prepreg sheet semi-cured by impregnation of an epoxy resin into a glass cloth substrate onto an internal layer circuit board having a circuit, and a copper foil is further laminated, followed by an integral molding through thermally compressing using a heated press.
However, in the step, since curing is conducted under a fixed pressure by reflow of an impregnated resin, it requires 1-1.5 hour for uniformly curing and molding and a long preparation step and, moreover, it requires a high cost because of costs of a multi-layered lamination press and glass-made cloth prepreg. In addition, it was difficult to exceedingly thin a thickness between layers because of a method impregnating a resin into the glass-made cloth.
In recent years, in order to solve such problems, there is watched a technology of a laminated printed circuit board by a buildup method without conducting thermal compression molding by a heat press and without using a glass-made cloth as an insulating material between layers.
In usual, as a method for a film-formation and film-rolling from an adhesive which is an insulating layer between layers, although there are formulated components such as a rubber-based compound, a polyvinyl butylal, a phenoxy resin, and a polyester resin, the components remarkably lower thermal properties in the laminated printed circuit board.
In a laminated printed circuit board prepared by the buildup method, in the case of employing a copper-laminated insulation sheet having an insulating resin layer formed on a roughened surface of a copper foil and in the case of employing a film-like insulating resin layer between layers in place of a tack dry prepreg sheet prepared by impregnating an epoxy resin into a glass-made cloth base material, workability is remarkably improved compared to a method in which an insulating resin layer between layers is formed by a prepreg.
However, there has been a problem in the cases that since there cannot be completely removed air bubbles remained at a boundary stair portion between an insulation base plate and a circuit in an internal circuit board, the air bubbles cause a deterioration of insulation and a deterioration of heat resistance in soldering and, further, peeling between layers is occasionally caused.
In order to prevent the air bubbles, lamination must be conducted under a condition of reduced pressure, and it requires a special equipment. Further, there have been problems that since a laminated insulation layer follows the boundary stair portion between an insulation base plate and a circuit in the internal circuit board, surface smoothness cannot be obtained, and inferiority in soldering is caused during mounting of parts or, a resist is peeled in a formation step of an etching resist, or a stable resist cannot be formed because of a cause of decline of pattern developability.
Still further, there become required surface via holes which carry conducting between layers and, when the surface via holes are formed by a mechanical drill, diameter of approximately 300 μm is a limit in hole processing and, under the limit, there are caused problems of precision in hole position and a drill life, etc.
In a conventional method in which a prepreg is prepared by impregnating an epoxy resin into a glass-made cloth and cured by heating and compressing using a press, and the surface via holes are formed by a mechanical drill, there are problems that it requires a high cost because of the use of the glass-made cloth, and ultra thin processing cannot be conducted, and fine processing cannot be conducted because of formation of surface via holes by a mechanical drill.
In order to solve the problems, there becomes required a photo-buildup method that there is formed a photosensitive insulating resin layer not having a glass-made cloth between layers on both surfaces or one surface of a material for an internal layer having patterning, micro surface via holes are formed by photo-imaging, and then, circuit is formed by etching through panel plating. For that reason, the photosensitive insulating resin layer between layers must be excellent in developability by a photographic method and, moreover, it must have a function as an additive adhesive.
In usual, in an additive method for the preparation of a board for circuit, thermosetting type additive adhesive has been employed, and methods in which an adhesive layer is roughened by an oxidant are enumerated in JP-B-88010752, JP-A-63297571, JP-A-64047095, JP-A-03018096 Official Gazettes. In the methods, the adhesive layer contains a rubber component such as an acrylonitrile-butadiene rubber, and surface of the adhesive layer is roughened by extracting the rubber component using a chromic sulfuric acid aqueous solution.
Further, there are proposed a method in which an adhesive layer is formed by dispersing an inorganic powder such as silica and calcium carbonate in a resin matrix such as an epoxy resin, a phenol resin, and a melamine resin which are excellent in heat resistance, and the adhesive layer is roughened by selective elution of the inorganic powder using a specified chemical substance, and a method in which there is dispersed a cured epoxy resin fine powder having different solubility to an oxidant into an epoxy resin matrix, and the cured epoxy resin fine powder is removed by selective elution using an oxidant, as disclosed in JP-A-01029479.
However, in the case of employing such the thermosetting type additive adhesive, it was not able to form the surface via holes by photo-imaging. In contrary, there are proposed a method in which an epoxy resin is employed as a matrix and a cationic photo-initiator is employed as a curing agent, and a method in which surface via holes are formed by photo-imaging through a method using an acrylate-modified product of a phenol novolak type epoxy resin or a cresol novolak type epoxy resin. However, since there are required adaptability to ultra high integration and high arithmetic speed, and high reliability, although there are required higher sensitivity and higher resolution, and there is required a material having low dielectric constant, high heat resistance, and low coefficient of linear expansion, a sufficient material is not still found.
In recent years, there has been investigated a laser-via method in which a hole having approximately 50 μm can be drilled by an eximer laser or carbon dioxide laser. As a composition for the method, a variety of compositions are investigated and, for example, a cationic polymerizable composition is known. In order to improve physical properties of a coating layer obtained from the composition, there has been investigated a method in which a variety of compounds are simultaneously employed.
However, in the composition containing an ionic catalyst, since storage stability is not excellent so much, as illustrated hereinabove in detail, although a various methods are investigated, sufficiently satisfied methods cannot be still found.
In more recently, a color liquid crystal displaying device is widely employed in an information equipment such as a computer displaying device, a telephone, and GPS, and home electric appliances, etc.
The color liquid crystal displaying device is prepared by, for example, a method in which a color filter for color separation is set up on a transparent base plate such as a glass plate, a transparent electro-conductive thin layer which is a transparent electrode such as indium tin oxide is prepared thereon by vapor deposition, and a transparent electrode is formed by patterning through a photolithography method, followed by setting up a thin layer for orientating a liquid crystal and further setting up the liquid crystal thereon.
Construction of the color filter is comprised, for example, forming picture elements on a transparent base plate, setting up a transparent electrode thereon, forming a protecting layer (also called an overcoating layer) on the picture elements in order to flatten surface of the picture elements and to prevent elution of impurities from the picture elements, and vapor-depositing a transparent electro-conductive thin layer thereon, whereby, the transparent electrode can be prepared by a photolithography method.
Accordingly, since the method requires thermal and chemical durability, the protecting layer must be set up on the color filter before vapor-depositing the transparent electro-conductive thin layer.
As properties to be required in the protecting layer for a color filter, there are enumerated transparency, thermal and chemical durability, adhesion to a transparent base plate and a color filter, thinness, coatability, smoothness, and hardness, etc. In the case of forming by vapor-depositing the transparent electrode onto the protecting layer and by a post treatment, since surface of the protecting layer is heated at 300° C. or so at maximum, heat resistance and discoloration resistance are required.
As such coating materials, JP-A-04202418 Official Gazette discloses a polyglycidyl(meth)acrylate-based resin and, JP-A-63131103 Official Gazette discloses a melamine resin, an epoxy resin, and a polyimide resin, etc., and JP-A-11035660 Official Gazette discloses a composition composed of a polymer containing not less than 50% of a specified cycloaliphatic epoxy acrylic ester, a curing agent, and a functional silane coupling agent.
However, the coating materials are not satisfied in various properties to be required including storage stability.
On the other hand, as a method for crosslinking and curing an epoxy compound within a short time of period by an ultraviolet ray and heat, an ionic polymerizable polymer composition is known. In order to improve physical properties of a coating layer from the composition, there have been investigated methods in which a variety of compounds are simultaneously employed.
Such an ionic curing system, particularly, a cationic curing system can be employed as a coating for metals and plastics and, in recent years, it is investigated in the use as the protecting layer for a color filter, etc.
However, since the composition containing an ionic catalyst is not good so much in storage stability, as illustrated hereinabove in detail, although various methods are investigated, sufficiently satisfied methods cannot be still found.
Furthermore, as a method for crosslinking and curing an epoxy compound within a short time of period by an active energy radiation such as an ultraviolet ray and heating, radical polymerization technologies and cationic polymerization technologies, etc. have been conventionally put into practice.
In the cationic polymerization technologies by the active energy radiation, since polymerization is not disturbed by oxygen in air, those do not have a limitation that polymerization must be conducted under an inert gas atmosphere, and those have an advantage that polymerization can be completely and quickly conducted in air. Nowadays, the cationic polymerization technologies are limited in polymerization of two kinds of monomers of an epoxy resin and a vinylether. Particularly, a photocurable type epoxy resin is excellent in an adhesive property, and a cured layer therefrom is fine in heat resistance and chemical resistance.
However, in conventional epoxy resins, polymerization speed is slower compared to a resin such as an acrylic acid derivative being capable of curing by radical polymerization, and it was problematic in a preparation efficiency of a product in which the resin is employed. On the other hand, the vinylether was problematic in that it is volatile and has a strong odor, and shrinkage is observed during curing compared to the epoxy resin, and adhesion is low, and it is not sufficient in water resistance and hydrolysis resistance.
In the cationic polymerization technologies by heating, a cationic polymerization catalyst is employed and, as the cationic polymerization catalyst, there has been widely investigated a method in which there is employed a thermally-latent catalyst in which activity of an acidic catalyst is temporarily suppressed and the activity is shown again by cleavage during thermally curing.
Further, in order to improve physical properties of a coating layer from the composition, there have been investigated methods in which a variety of compounds are simultaneously employed.
Such the ion curing, particularly, the cationic curing system can be utilized as a coating for metals and plastics and, in recent years, it is investigated in the use of coating for metallic cans and plastic film-coated metallic drawn cans.
As such the thermally-latent catalyst, as illustrated hereinabove in detail, although various methods are investigated, sufficiently satisfied methods cannot be still found.
On the other hand, as described in J.M.S.-PURE APPL. CHEM., A32(10), PP. 1699-1707 (1995), etc., although oxetane itself has slow cationic polymerizability, initial reactivity can be largely improved by employing together with a cycloaliphatic epoxy compound, etc. It is more excellent than in cationic polymerizability of the epoxy compound alone, and it is exceedingly useful to employ the oxetane together with the epoxy compound from a viewpoint of curing rate.
The present inventions (i) and (ii) provide a curable resin composition for a coating which is excellent in storage stability, in which curing quickly proceeds at a higher fixed temperature than a room temperature and curing does not proceed so much at the room temperature, and provide a method for the preparation thereof and a coated article which is excellent in heat resistance, staining resistance, a removal property of staining substances, and a abrasion resistance, etc.
The present invention (iii) provides an insulating resin composition for a laminated printed circuit board by a buildup method which is most appropriate for a laser-via, in which it is quickly cured at a temperature higher than a fixed temperature, and it is excellent in storage stability at a room temperature level, and temperature dependence of volume resistivity after curing is small, and provides a laminated printed circuit board.
The present invention (iv) provides a curable resin composition which can be cured at a temperature higher than a fixed temperature, and it is excellent in storage stability at a room temperature level and, in which an electric insulation property of a resin does not fall so much after curing, and provides a protecting layer for a color filter which is excellent in transparency, thermal and chemical durability, adhesion to a transparent base plate and a color filter, thinness, coatability, smoothness, and hardness, and provides a color filter in which the protecting layer for a color filter is set up and a liquid crystal displaying equipment having the color filter.
The present invention (v) provides a curable resin composition for a coating, which can be quickly cured at a temperature higher than a fixed temperature, and which is excellent in storage stability at a room temperature level and, in which initial reactivity is improved, and provides a method for the preparation thereof and a coated article using the curable resin composition.